My v1 was stainless steel. I think it's a waste of money so I went with aluminum this time around. (And I don't have a lot of price sensitivity; I normally buy what I want. But in this case, there is zero practical difference IMO)
It would be one thing if Apple Watch is a mature product with some staying power after your purchase, but it's not. Apple is clearly still on a market discovery path with Apple Watch.
Plus, I like the aluminum black too given how big the Apple watch is, it makes it a bit more subtle on the wrist.